Composite structures are widely used in high performance applications because of their light weight, high strength, high stiffness and superior fatigue resistance. These structures broadly comprise a combination of dissimilar constituent materials bonded together by a binder, but are most commonly formed by a thermosetting resin matrix in combination with a fibrous reinforcement, typically in the form of a sheet or mat. Multiple plies of the matting are impregnated with a binder such as epoxy plastic resin or polyester resin, and formed into a “layup”. Pressure and heat are applied to the multi-layer part layup in order to compress and cure the plies, thereby forming a rigid structure.
Certain features of composite structures, such as non-uniform or complex surface geometries, complicate the compaction process. In order to satisfy tight tolerances and/or achieve complex surface geometries, specially made tools, sometimes referred to as pressure intensifiers, are used to direct pressure to those surface areas which are tolerance critical or possess special geometries. These pressure intensifiers also serve to distribute the applied compaction pressure over the surface of the layup in a desired manner, particularly where source of pressure is derived from vacuum bagging.
In the past, the pressure intensifiers described above were often fabricated from an elastomeric material formed into the shape of the tool using a mold. It was thus necessary to fabricate the mold, and then prepare it by cleaning the mold surfaces and applying a release coating. The elastomeric material had to be mixed and poured into a heated mold, and then cured and sometimes surface finished before it could be used. The entire molding process was therefore relatively time and labor intensive. The resources needed to fabricate and prepare the mold represented substantial manufacturing costs in the case of short production runs, such as those encountered in the aircraft industry, for example. In addition, the dimensional accuracy the molded type intensifier tools was sometimes less than desirable. This is because molded features of the tool depend on the accuracy of the mold cavity, the cleanliness of the mold, the potential introduction of voids into the molding material, part shrinkage and other factors.
Accordingly, there is a need in the art for an improved method of manufacturing a pressure intensifying tool which overcomes the deficiencies of the prior art discussed above. The present invention is directed toward satisfying this need.